The present invention is generally directed to stator cores used in motor assemblies. In particular, the present invention is related to an insulated stator core with improved electrical performance properties. Specifically, the present invention is related to an insulated stator core with attachment features.
Use of motor assemblies to rotate fans inside blowers is well known. To facilitate assembly of the blower assembly, the stator may be mounted directly to a circuit board. In particular, a completed stator assembly with windings is secured to the circuit board using threaded screws. Next, the windings are electrically connected to the circuit board which provides the ability to control the amount of electrical energy generated by the motor assembly. A rotor cup is then coupled to the stator assembly in a well known matter. When energized, the rotor turns a shaft which may have a fan connected thereto or the shaft may be used to drive some other piece of equipment.
The motor""s operation is critical to the performance of the blower assembly. As such, a primary area of concern is the operation of the stator and how it is assembled. Currently, stators are made of a stack of steel laminations of a predetermined thickness. These laminations are precisely stacked and then secured to one another. This may be done by using rivet assemblies which extend through the stack and which may also function as stand-off posts for assembly to the circuit board. Alternatively, the stack may be welded in a well-known manner so that all the pieces are secured to one another. Stand-off posts may then be riveted, welded or otherwise fastened to the stack for assembly to the circuit board. In any event, after the stack laminations are secured to one another, the inner diameter and outer diameter of the laminations and the ends of the posts are masked off and an electrostatic epoxy powder is applied. The epoxy powder is then applied and cured so as to provide insulating features for the stator assembly prior to winding. The curing process takes about two hours.
One experienced in the art of motor assembly will realize several problems with the aforementioned stator assembly process. One significant problem is that the steel lamination stack may become skewed during assembly. As a result, the dimensional properties of the stack become distorted and the ability to wrap the required number of wire windings around the different poles of the stack is hampered. In particular, if the stack is skewed the windings will not fit between the stator teeth. And if a maximum number windings are not obtained the motor""s performance is severely diminished. In addition to taking a long time to cure the epoxy material, the cured epoxy may provide inadequate coverage which results in electrical xe2x80x9ccreepagexe2x80x9d between the windings and the exposed areas of the stator. This electrical creepage may reduce motor life and otherwise adversely effect motor performance. The epoxy curing process is also problematic inasmuch as the epoxy powder may have pin holes or may collect dust during the curing process and result in poor insulating properties for the motor assembly. Moreover, the applying of epoxy powder may result in thin areas which tend to flake after curing which also leads to shorting problems. The epoxy powder must be delivered in a refrigerated truck and stored at a temperature of 75xc2x0 F. or below to prevent deterioration. It must also be stored in a moisture-free environment for proper flow and adhesion. Running the epoxy coating machine in humid climate conditions causes the epoxy powder to cake, thus causing the machine to jam, creating expensive down time.
It has been recognized that the aforementioned shortcomings reduce the quality of the stator assembly and, as such, the overall quality of the motor assembly is not what it could be. Nor does the current manufacturing process lend itself to high quality assemblies. Several attempts have been made to overcome the quality problems by applying more epoxy material to the desired areas. However, the thickness of the epoxy material cannot be uniformly controlled and it also reduces the number of windings that can be wound around the stator core. Another attempt to overcome such problems includes the use of a two piece insulator wherein one piece covers a portion of the stator assembly and the second piece covers the remaining portions. However, these insulators have been found to significantly narrow the winding gap so as to diminish the ability of the stator to perform its desired function. Moreover, the two piece insulator devices are very expensive to tool and to assemble. And, if the two piece insulators are misaligned during assembly, the aforementioned creepage problems arise.
Therefore, there is a need in the art to provide an insulated stator assembly which has improved electrical performance properties and reliability. There is also a desire in the art to improve the manufacturing process of the stator assembly and to provide the stator with features that otherwise enhance the overall assembly process of the motor assembly.
Therefore, it is a first aspect of the present invention to provide an insulated stator core with attachment features.
Another object of the present invention, which shall become apparent as the detailed description proceeds, is achieved by an encapsulated stator assembly, comprising a plurality of like laminations stacked in registration with one another, each lamination contacting at least one adjacent lamination, but laminations are not integrally connected in any way to any other lamination; and a single covering layer partially enclosing and maintaining in registration the plurality of like laminations.
Other aspects of the present invention are attained by a blower assembly, comprising a housing having an inlet and an outlet; a fan assembly carried in the housing for drawing air into the inlet and exhausting the air out the outlet; a control circuit board carried by the housing; and a motor assembly for operating the fan assembly, the motor assembly having a rotor assembly coupled with a stator assembly that is partially encapsulated by a covering layer, the covering layer having at least one post extending therefrom that is mountable to the control circuit board.
Still another object of the present invention is attained by a method for manufacturing an insulated stator, comprising: providing a pair of mold halves with a keyed mandrel extending through the halves when closed; stacking a plurality of laminations in registration with each other, but unsecured to one another into the mold halves and onto the keyed mandrel; closing the mold halves onto the plurality of laminations; injecting a polymeric material into the mold halves to dispose a covering layer about the plurality of laminations so as to secure the plurality of laminations to one in another while maintaining their registration with one another; and opening the mold halves and ejecting the plurality of laminations with the covering layer.
These and other objects of the present invention, as well as the advantages thereof over existing prior art forms, which will become apparent from the description to follow, are accomplished by the improvements hereinafter described and claimed.